Paul, what is involved in converting to a 70A or is it even feasible?
Carl
KM1H
----- Original Message -----
From: "Paul Christensen" <w9ac@arrl.net>
To: <amps@contesting.com>
Sent: Wednesday, December 23, 2009 1:29 PM
Subject: Re: [Amps] water cooling tips
>> "Pure DI water can get as resistive as 18 Megohm-cm, which is about the
>> theoretical limit. This water would be very difficult on fittings and
>> metals as it will scavenge ions, which causes migration through the
>> hoses,
>> and can plate the metal ions elsewhere. It is very difficult to maintain
>> this perfect water in this condition, as it degrades as it strips
>> whatever
>> ions it can through the cooling system. You don't want pure DI water, but
>> a compromise between 100 kilohm-cm and a few Megohm-cm is appropriate for
>> most high voltage systems that need cooling."
>
> John,
>
> Any idea where off-the-shelf distilled water falls in relation to these
> figures? I use an Alpha 70V with the better branded water (e.g.,
> Zephyrhills). I once purchased "brand X" water off the shelves at
> Walgreens
> and the leakage current indicator went off the scale. Either they had a
> QC
> problem, or tap water was being re-labeled and sold as distilled. I had
> to
> flush the system out a few times, but leakage went back down to about 1 mA
> @
> 4KV, a normal value for the amp.
>
> Recently, all the 70V plumbing was replaced (after almost 40 years) and
> the
> overall leakage now is so low that the logic board sometimes interprets it
> as having an empty reservoir. The entire plumbing system was replaced
> with
> original JACO Polypropylene parts, still in plentiful supply at industrial
> plumbing retailers. Total cost of the rebuild, together with a short
> section of new 1/4' copper pipe was about USD $15.00. I have not done
> anything to the condenser other than flush it out. I would say that the
> cost of ownership with this amp over its 40 year life span has to be at
> the
> extreme low end of the scale, notwithstanding the dearth of available CV
> tubes.
>
> Paul, W9AC
>
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